(a) Payments required to be made by an authority under a contract for effective interest rates under this subchapter shall be payable from the same revenue source or sources from which the related bonds are payable.
(b) Revenues derived by an authority from a contract for effective interest rates shall be used for one (1) or more of the following purposes:
(1) The payment of the bond principal, bond premium, interest on the related bonds, or for amounts held in reserve for the bond payment;
(2) The payment of the authority's obligations under the contract; or
(3) Any purpose for which the related bonds were or could have been issued if the contract is authorized by the governing body of the authority in the same manner as the issuance of bonds.